1. Field of the Invention
The present invention relates to a method and device for measuring contour such as surface roughness and the like and, in particular, to such a method and device which is used to measure the surface roughness and the like of a work having a curved shape.
2. Description of the Related Art
Conventionally, a surface roughness and contour measuring machine includes several types of measuring machines as follows:
A. A measuring machine in which an average height in the front and rear portions of the measured length of a work is found, an average straight line is found from the average height value, and the average straight line is subtracted from a measured curved line so as to find the surface roughness of the work.
B. A measuring machine in which an average straight line is obtained by a method of least squares over the whole measured length of a work, and the average straight line is subtracted from a measured curved line so as to find the surface roughness of the work.
C. A measuring machine used for measuring a work having a circular arc shape, in which the radius of curvature of the work is previously obtained and circular arc component is removed from a roughness curved line according to an equation of circle so as to find the roughness of the work.
D. A measuring machine in which a circular-arc-shaped reference surface is prepared and a detector is moved to follow the reference surface to thereby remove a circular arc component so as to find the roughness of the work.
However, in the above-mentioned A and B types of measuring machines, the curved surface shape of a work cannot be corrected and, therefore, it is impossible to measure the roughness of the curved surface shape of the work. Also, in the C and D types when the radius of curvature of a work is not known, it is impossible to measure the roughness of the work surface. Further, the C and D types of measuring machines cannot be applied to other works than those having a circular-arc-shaped curved surface. In addition, in the C and D types of measuring machines, the center of the drive part of a contact pointer must be matched with the center of a reference surface having a circular arc shape, but such matching or alignment is difficult.